Levels of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins anddibenzofurans in commercial yoghurt samples in Spain - Comparison with different dairy products

A method developed previously for the simultaneous analysis of polychlorina ted biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychl orinated dibenzofurans (PCDFs) in powdered full fat milk is now examined fo r their determination in yoghurt. The results of this study are consistent with those found for PCBs and PCDD/Fs in powdered full far milk. The method ology is based on the matrix solid-phase dispersion of the freeze dried yog hurt enabling the extraction of the neutral and apolar lipids of the matrix . Mean recoveries were above 94% for the studied coplanar PCB congeners spi ked at the typical reported levels for dairy products and above 92% for the spiked C-13(12)-PCDD/Fs. The validated methodology was applied to the PCB and PCDD/F analysis in full fat and low fat yoghurts form different brands commercialised in Spain. In all cases, levels detected in the low fat yoghu rts analysed were several rimes higher than those found in the full fat yog hurts when reported on a fat basis (between 3.3 and 11 times for PCBs and b etween 3.3 and 45 times for PCDD and PCDF homologue groups). In general, th is discrepancy applied also for the toxic 2,3,7,8-TCDD equivalents (TEQs) c alculated in each case. The calculated TEQs (on a fat weight basis) from PC Bs and PCDFs in the low fat yoghurts were higher than those reported previo usly for different Spanish dairy products, including liquid and powdered mi lk and butter. Nevertheless, the estimated daily intake (DI) for low fat yo ghurts was lower than those calculated for the rest of the dairy products i nvestigated. This apparent contradiction showed that the regulation of PCB and PCDD/F contents should be based on DIs rather than on TEQs reported on a fat-adjusted basis. Finally, the feasibility of differentiation among dif ferent dairy products, i.e. liquid and powdered milk, butter and yoghurt, o n the basis of their respective PCB and PCDD/F patterns by using multivaria te methods, has been shown. (C) 1999 Elsevier Science B.V. All rights reser ved.